Combined wireless sending and receiving system



Nov. 16 1926;

A.' NYMAN COMBINED WIRELESS SENDING AND RECEIVING SYSTEM Filed July 15. 1920 INVENTOR fi/amnaer WITNESSES:

/1/ man BY y paw Q-T' nJQ ATTORNEY Patented Nov. 16, 1926.

UNETE. STATES ever ALEXANDER NYMAN, OF 'WILKINSBURG, PENNSYLVANIA, ASSIGNOR TO WESTING- HOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION OF PENNSYL- VAN IA.

COMBINED WIRELESS SENDING AND RECEIVING SYSTEM.

Application filed July 15, 1920.

My invention relates to systems for simultaneously sending and receiving messages on the same apparatus, so that the same antenna may be used to both send and receive without necessitating switching.

More particularly, my invention relates to an apparatus for simultaneously sending and receiving radio messages and to the use of a double antennae so arranged that there is a condenser action between the two branches, thus permitting the received oscillations to be caught, and to means whereby the sending of a message will not interfere with the simultaneous use of the apparatus as a receiving station.

In the past, changing a wireless apparatus from a sending to a receiving station has involved the act of switching. It has been difficult to both send and receive at the same time, if communications were being transmitted and received from the same station, for the reason that the waves sent from the home station are tuned to the length of those received and the receiving apparatus responds to both. It has not been possible to successfully send and receive simultaneously under the above outlined conditions.

This invention is conceived with the idea of rendering the simultaneous use of a wireless apparatus, both as a sending and a receiving station, feasible, and, at the same time, to accomplish that result while using the same antennae. Heretofore, attempts have been made to use two sending antennae and to locate a third receiving antenna between the two, at such a position that the radio oscillations in the two sending antennae reacted at the position of the receiving antenna to produce the node of a standing wave. This method has been found highly impracticable because it has proved diflioult to locate the exact position for the receiving antenna. Moreover, since the distance apart of the two antennee to produce a standing wave varies with the wave length, it has been necessary to move the antennae. By my disposition of apparatus, no careful adjustment of the distance between the antennae is necessary and no third antenna need be used.

An object of my invention is to provide for sending and receiving wireless Serial No. 396.531.

binations to be hereinafter set forth and claimed, with the understanding that the several elements comprlsing myinvention may be varied in their proportions and arrangement, without departing from the spirit and scope of the appended claims.

In order to make my invention more clearly understood, I have shown, in the accompanying drawings, means for carrying it into practical effect, without limiting the improvements in their useful applications to the particular constructions, which, for the purpose of explanation, have been made the subject of illustration.

Figure 1 is a diagrammatic View of a complete sending and receiving station;

Fig. 2 is a diagrammatic view illustrating he flow of current in the receiving apparatus;

Fig. 8 is a diagrammatic View illustrating the flow of the current in the sending apparatus.

In the drawings, referring particularly to Fig. 1., I have shown a double antenna 1, the two branches of which are connected to a variable inductance 2. In shunt through the inductance 2 is a circuit containing a variable capacitance 3. The inductance 2 and its capacitance 8 may be varied to tune the receiving circuit to any desired length of waves.

At the middle point of inductance 2 is a lead, as indicated at 4, which is connected to a variable inductance 5 and, through a capacitance 6, to the ground. Connected across both sides of the variable inductance 5 is a variable capacitance 7 and, by changing the values of the inductance 5 and the capacitance 7, the sending circuit may be tuned to any desired wave length. In circuit through the inductance 5 and the capacitance 6 is. a filament element 8 and a plate element 9 of an electron tube 10 having a grid element 11 connected to the m ductance 5 so that there is the necessary feed back between grid and plate circuits for sustained oscillations.

.e suitable battery ilfi'prevides current in inductive relation to the inductanc .cuits of tubes used as detectors.

heating the filament element 8. rangement is the customaryone for using an electron tube as a generator of radiofrequency alternating current. 1

In circuit with the plate circuit oi the electron tube is a plate 13 and a filament 14 of an electron tube 15, acting as a modulator and having a grid element 16. The filament 14 is heated by means of a suitable battery 17. Within the plate circuit Ol' modulator tube 15 is an inductance 18 that is so that there will be power absorption necessary to modulator action. A C battery 19 is provided in circuit with the grid 16, the n egatve terminal of which applies its potential to the grid 16. lVithin the grid circuit is located an inductance 20. lVithin the circuit 01 the two electron tubes 10 and 15 is provided a generator 19 having a high reactance coil 20 that acts as a constant source of current and delivers tor tube 10.

Coupled inductively power tothe genera-- because of the inductive coupling of the inductances 20 and 21 and this variation of potential of the grid 16 causes the tube 15 to absorb power in accordance with the change of potential.

While, for convenience of illustration, 1 have shown a generator tube coupled with a modulator tube as a generator of radiofrequency oscillations the amplitude of which is controlled by the voice, any method of generating sending oscillations maybe used, such as the Poulsen are or the highlrequency generator, and it is to be expressly understood that my invention is not limited to any particular type oi? apparatus for generating the radio-frequency waves to be transmitted.

inductively coupled to the inductance 2 is an inductance 2% so placed that the cur rents flowing in either direction through the inductance 2 from the point l will exactly balance in their effect uponthe inductance 24, and thus, oscillations set up in the sendin circuit will induce no oscillations in the receiving circuit. In circuit with the inductance 24% is a variable capacitance 25 and a stopping condenser 26. An electron tube 27, acting as a detector and having a. grid element 28, a plate element 29 and a filament element 30, is in circuit with the inductance 2el. In circuit across the condensers 26 and 25 is a resistance 31 that performs the function of the customary grid leak in grid cir- To heat filament 80 an A battery 32' is provided. The amount of current flowing through the The arfilament is controlled by the insertion of a variable resistance 32. Within the. plate circuit oi the electron tube 27 are located telephone receivers 33 having a capacitance 3 L shunted between them. A suitable l3 battery 35 applies positive potential to the plate 29.

There should be no mutual inductance, as will be apparent, between ceitain of the coils. To obviate this mutual inductance, these coils may be placed at right angles to each other. To avoid the etl'ect of stray lield upon the coils, they may be encased within metal containers or boxes. It is necessary to the efficient operation of this system that the inductance shall be tree from the eliect oi stray fields and that certain of the coils shall. not have mutual inductance between them, and any suitable methods may be employed to obtain these results, the above outlined methods being but two of many that may be employed.

ll ireless messages may be received as indicated diagrammatically in Fig. 2. The two branches of the antenna 1 act as capacitance and, with the inductance 2, form a circuit which, when properly tuned, will be responsive to the received oscillations. The received oscillations will flow in this tuned resonant circuit as indicated by the arrows. The received impulses induce oscillations in the inductance 2 1 by reason of its inductive relation to the inductance 2. This induced current acts to affect the potential of the grid 28 of the elect2on tube 27, and, as

the proper conditions for use of this tube 2? as a detector are present, oscillations are set up in the plate circuit corresponding to the received oscillations, and messages may be taken through the telephone receivers 33. By virtue of adjustment of the variable capacity 25, the circuit may be tunedL to any desired frequency. it is obvious that any method. of detecting the received oscillations may be employed, and that l have shown an electron tube used as a detector of radio-frequency current solely for purpose of illustration and to make clear the utili ty of my invention and its application to the problems of radio communication.

The oscillations in the sending circuit take place as diagrammatically illustrated in Fig. 3, in which the oscillations induced in the inductance 5 pass up through the mid-point l oi the inductance 2 and flow in opposite directions out through the branches of the antenna 1.

The lnductance 24E of the receiv circuit is so located that the two portions of the current flowing in opposite directions in the inductance 2 exactly balance each other, and there is a zero inductance effect within the coil 24-. The tube 10 is arranged to act as a generator of radio-frequency current, there being mutual inductance between the plate and grid circuits. The capacity 7 isvariable and, likewise, the inductance 5 may be made of variable quantity so that the sent oscillations may be tuned to the desired frequency. The tube 15 acts as a modulator of the radio-frequency current generated by the generator tube 10. The microphone 25 causes oscillations of audio frequency in inductance 21 and this, in turn, induces oscillations of audio frequency in inductance 20. By reason of the change in grid potential of the grid 16, audio-frequency oscilla tions are set up within the plate circuit of the modulator tube 15. In accordance with well known principles of radio transmission, the audio-frequency oscillations absorb power from the input to the antenna and thus the audio-frequency oscillations will affect the amplitude of the radio-frequency oscillations sent out. This produces the audio pulses necessary for the transmission of a message.

From the foregoing it will be apparent that, by reason of the double antenna acting as capacitance, upon receiving radio oscillations, a current is set up through the inductance 2, and hence, the inductance 2a of the receiving station has the received oscillations impressed upon it. Furthermore, the sent oscillations are made to enter the inductance 2 in such manner that they induce equal and opposite currents in the coil 24, with a result that zero current flows in the inductance 24. Therefore, the station may be used simultaneously for both sending to, and receiving from the same or different stations without switching and without interferences or confusion in signals.

While I have described but one embodiment of my invention, it is apparent that.

the distance between said antennae being such that the electrostatic capacity between them is a substantial portion of the reactance of the circuit including said inductor and upright antennae, and means for tuning said circuit, whereby said inductor, antennae and the capacity between said antennae may be rendered resonant.

2. In an antenna system, adapted for sending and receiving, a pair of antennae, there being a substantial electrostatic capacity between said antennae, an inductor connecting said antennae whereby a nodal point is located in said inductor, a connection from said nodal point to ground, a sending device cooperating with said connection, a tuning means in shunt with a portion of said inductor including said nodal point, whereby the capacitance between said antennae, the inductance of said inductor and the reactance of said tuning means may render the circuit including said antennae, inductor and capacitance resonant, and a receiving device energized from said resonant circuit.

3. In a radio system, a resonant circuit including two antennae, a capacitance between them and a reactive connection counter-balancing said capacitance, a sending device connected between the ground and that point of said resonant circuit which does not change its potential as a consequence of the oscillations to which it is resonant and a receiving device energized from said resonant circuit.

4. In a radio system, a resonant circuit including two antennae, a capacitance between them and a reactive connection counter-balancing said capacitance, at sending device connected to said resonant circuit at the mid-point of said reactive connection to produce a balanced system and a receiving device energized from said resonant circuit, the sending circuit being tuned to a frequency of the frequency in said resonantcircuit.

In testimony whereof, I have hereunto subscribed my name this 10th day of J uly,

ALEXANDER NYMAN. 

